When to use a hardener when processing B&W film

[xkaes]

Normally I either add a hardener to the fixer/hypo or leave it out completely. I've never thought much about other alternatives. Assuming you want to use a hardener (which is a completely different discussion) what would be the PROS and CONS of using these approaches:

#1: Treat the film with the hardener before the fixer
#2: Add the hardener to the fixer
#3: Treat the film with the hardener after the fixer but before a wash to remove the fixer
#4: Treat the film with the hardener after the fixer and after a wash to remove the fixer


What I can think of are:

#1 -- longer fixing times
#2 -- shorter fixing times
#3 -- even faster fixing time
#4 -- shorter washing time

[Doremus Scudder]

#1: Treat the film with the hardener before the fixer
Superfluous step when you can just go from the stop to a hardening fixer. Why invest time and more handling in an extra step.


#2: Add the hardener to the fixer
This has been the standard operating procedure for decades. Unless there is a reason to harden the emulsion before developing/stopping (e.g., high-temperature processing), this seems most practical and entails the fewest steps.


#3: Treat the film with the hardener after the fixer but before a wash to remove the fixer
Superfluous also, when you can just use a hardening fixer. Hardener does not affect the fixation significantly, so why not do both at the same time?


#4: Treat the film with the hardener after the fixer and after a wash to remove the fixer
I don't see the point of this. Usually hardener is there to protect the film when handling. After the wash all you have to do is dip it in wetting agent and hang it to dry; not much handling left.




What I can think of are:

#1 -- longer fixing times
I have never seen different fixing time recommended for hardening and non-hardening fixer. I don't think the hardener makes any significant difference. Adding 10% to the fixing time is inconsequential. I doubt if there is even that much of an increase.


#2 -- shorter fixing times
#3 -- even faster fixing time
See above.


#4 -- shorter washing time
Washing times can be shorter without hardener in the process. A treatment in a wash aid (e.g., Hypo Clearing Agent) will speed up the wash. The HT-2 test can give you information on the minimum wash times, and the ST-1 or the selenium-toner test can give you info on adequate fixation. I'm sure you're familiar with these. It shouldn't be hard to see if hardener affects fixing times or how much longer you need to wash with hardener in the process.

Of course, you shouldn't use hardener in your film developing sequence unless it is necessary, e.g., soft-emulsion films that are getting damaged during processing or high-temperature processing, etc.

Note that Kodak and others recommend using a hardener before development for high-temperature processing. Here's the salient paragraph from the Kodak Formulas booklet (1973):

"At higher temperatures, the use of KODAK Prehardener SH-5 before development will harden the emulsion sufficiently to allow use of normal solutions and processing procedures, even at temperatures as high as 43°C (110°F). Full instructions for use, including adjustment of developing time for various temperatures, are given with the prehardener formula in the "Formulas" section.
The use of the prehardener is the simplest and safest procedure for processing at high temperatures..." (the text continues to describe adding sodium sulfite to the developer in lieu of hardener.)

The formula for the prehardener is:

"KODAK Prehardener SH-5

Solution A
Formaldehyde, about 37% solution by weight ---- 5 ml
Solution B
Water -------------------------------------- 900 ml
*0.5% solution of KODAK Anti-Fog, No.2
(6-Nitrobenzimidazole Nitrate) ----------------- 40 ml
KODAK Sodium Sulfate (anhydr.) --------------- 50 g
KODAK Sodium Carbonate (monohydr.) --------- 12 g
Water to make -------------------------------- 1 liter

*To prepare a 0.5% solution, dissolve 1 gram of KODAK Anti-Fog, No. 2, in 200 ml of water.

Directions for mixing: The working solution should be prepared just before use by adding 5 ml of Solution A to 1 liter of Solution B and mixing thoroughly.

Directions for use: Bathe the exposed film in KODAK Prehardener SH-5 for 10 minutes with moderate agitation. Then remove the film from the solution, drain fro a few seconds, immerse in in water for 30 seconds, drain thoroughly, and immerse in the developer. In general, up to 32°C (90°F), conventional developers such as KODAK Developer D-76, DK-60a, D-19, etc, can be used without modification.
Times of development will be about as follows:

Temperature--- % of Normal Development Time*
24°C (75°F) ------ 100%
26.5°C (80°F) ----- 85%
29.5°C (85°F) ----- 70%
32°C (90°F) ------- 60%
35°C (95°F) ------- 50%

*Normal development time recommended when the developer is used at 20°C (68°F) without a prehardener.

Following development, rinse, fix in an acid hardening fixing bath [! NB], wash and dry in the usual way.

At Temperatures Above 35°C (95°F): Increase the concentration of KODAK Anti-Fog, No. 2, in the prehardener, using as much as double the normal formula concentration, if necessary, to control fog. Process as before, using a low-activity developer, such as KODAK Developer D-76, to avoid excessively short development times. The average development time at 443°C (110°F) after prehardening is about one quarter of the normal time at 20°C (68°F) .
In case the development time at elevated temperatures is too short for practical use, sodium sulfate can be added to the developer to extend the time of development.

Keeping Properties and Useful Capacity: The keeping properties are adequate for ordinary tray and tank practice. Gradual deterioration does occur on standing, but the bath will keep satisfactorily, if unused, in a closed bottle for 3 or 4 weeds at 35°C (95°F). For most applications, the useful capacity without replenishment is more than ten 8x10-inch (20.c x 25.4-centimeter) films per 946 milliliters (1 quart) without serious change in properties."

I don't know how readily available 6-Nitrobenzimidazole Nitrate is, or whether you could substitute BTA for it in the formula. Maybe some chemists here will add to the discussion.

Hope this helps,

Doremus

[Alan9940]

Doremus provides a through and complete reply, but if you decide to keep it simple by using a hardening fixer I've used the F-6 formula for years:

Water (at about 100F) 600ml
Sodium Thiosulfate (penta) 240g
Sodium Sulfite (anhy) 15g
Acetic Acid (28%) 48ml
Sodium Metaborate 15g (or Borax)
Potassium Alum 15g
Water to make 1L

Or, if you don't want to mix it yourself just buy some standard Kodak Fixer (powder) or Kodak Rapid Fix w/hardener. Don't know if Kodak chemistry is readily available, yet (given recent issues), but I believe it will return soon.

[Michael R]

Kodak Rapid Fixer + hardener has returned and should be available.

One caution regarding F-6 if the goal is hardening a non-hardened emulsion... it provides less hardening than F-5. The more acidic the environment, the more effective the alum hardener. The substitution of boric acid in F-5 with borate alkali to make F-6 raises the pH of the fixer, so you get significantly less hardening action.


Doremus provides a through and complete reply, but if you decide to keep it simple by using a hardening fixer I've used the F-6 formula for years:

Water (at about 100F) 600ml
Sodium Thiosulfate (penta) 240g
Sodium Sulfite (anhy) 15g
Acetic Acid (28%) 48ml
Sodium Metaborate 15g (or Borax)
Potassium Alum 15g
Water to make 1L

Or, if you don't want to mix it yourself just buy some standard Kodak Fixer (powder) or Kodak Rapid Fix w/hardener. Don't know if Kodak chemistry is readily available, yet (given recent issues), but I believe it will return soon.

[xkaes]

I've generally always used hardener in the fixer, but I've been using it less and less for various reasons, and since I mix my own, I began to wonder -- If I do use it, when is the best time? I was under the impression that hardening the emulsion increases the fixing time and the washing time.

[Tin Can]

Lol

[xkaes]

Superfluous also, when you can just use a hardening fixer. Hardener does not affect the fixation significantly, so why not do both at the same time?

I have never seen different fixing time recommended for hardening and non-hardening fixer. I don't think the hardener makes any significant difference. Adding 10% to the fixing time is inconsequential. I doubt if there is even that much of an increase.

Doremus



Here's what Stephen Anchell (second edition) says -- that adding hardener to the fix can double the fixing time.

250213


That makes sense to me. So why not an extra step of hardening after fixing.

I'm thinking of doing the hardening after the washing to remove the fixer -- because the hardener also extended the wash to remove the fixer.

So shorter fixing times and shorter wash times if the film is hardened last -- or not hardened at all.

[Vaughan]

I'm thinking of doing the hardening after the washing to remove the fixer -- because the hardener also extended the wash to remove the fixer.

So shorter fixing times and shorter wash times if the film is hardened last -- or not hardened at all.

Usually the hardener is needed to ensure the gelatine will survive processing, which includes the wash which is often the longest wet step. Hardening after the wash is closing the door after the horse has bolted.

You'll need to consider the time needed to wash the hardener solution out.

[Michael R]

I’m not sure why one would use a hardener with most films unless processing (wash) temperatures are high and/or there is a high risk of mechanical damage during washing.

A hardening fixer generally requires both longer fixing and longer wash times. For an example see Ilford’s instructions for using Hypam with a hardener (the normal film processing rapid fixer time range is doubled). Ilford advises not to use a hardener with most films under normal circumstances and advises not to use a hardener with papers.

If one is determined to use a hardener follow the manufacturer’s directions (Kodak Rapid Fixer with Hardener, for example).

[Bill McMannis]

I am far from being an expert despite having processed a few thousand 35mm rolls and hundreds of 4x5’s over five decades. My one observation is if I skip hardener, my negatives dry flatter making for better enlargements or scans.

[xkaes]

A hardening fixer generally requires both longer fixing and longer wash times. For an example see Ilford’s instructions for using Hypam with a hardener (the normal film processing rapid fixer time range is doubled).

That's what I had assumed, but others are of a different opinion -- see Post #2 -- hence my original question, which is IF I use a hardener, when is the best point to use it? Since the hardener makes fixing (and washing the fixer out) longer, why not harden after that is all done.

[xkaes]

I am far from being an expert despite having processed a few thousand 35mm rolls and hundreds of 4x5’s over five decades. My one observation is if I skip hardener, my negatives dry flatter making for better enlargements or scans.

I've never done a direct comparison, but I would not be surprised if this is the case.

[Michael R]

That's what I had assumed, but others are of a different opinion -- see Post #2 -- hence my original question, which is IF I use a hardener, when is the best point to use it? Since the hardener makes fixing (and washing the fixer out) longer, why not harden after that is all done.

The best point to use it depends on the conditions during the various steps of the process. For example if one expects the whole process to be at a high temperature - say >85F, a pre-hardener would sometimes be used and/or sodium sulfate added to the developer etc. If the conditions in the wash or during drying were potentially going to damage an unhardened emulsion (high temperatures, mechanical damage), a hardening stop bath or fixer could be used. Etc. I suppose you could use a hardening bath after the wash, but note you would obviously need to re-wash after the hardener.

[xkaes]

I assume that removing the hardener "residue" with a wash is pretty quick. After all, you want to hardener to stay in the film, don't you?

[Michael R]

I assume that removing the hardener "residue" with a wash is pretty quick. After all, you want to hardener to stay in the film, don't you?

If you use a traditional alum hardener the solution is highly acidic. You want a thorough enough wash afterward to remove the hardening solution. The hardener is not something you can wash out. The alum compound in the hardening solution causes the cross-linking of the gelatin molecules (in a similar way that tanning developers do), which makes the gelatin less water-soluble (ie more heat-resistant), more resistant to swell, and more resistant to physical damage when wet. None of this really helps anything once the film is dry. Most contemporary films are pre-hardened which means traditional hardening procedures during processing don’t do very much anyway.

[Doremus Scudder]

That's what I had assumed, but others are of a different opinion -- see Post #2 -- hence my original question, which is IF I use a hardener, when is the best point to use it? Since the hardener makes fixing (and washing the fixer out) longer, why not harden after that is all done.

xkaes,

I'm obviously in error about hardener not affecting fixing times too much. So, yes, that would be a consideration.

This whole conversation begs the question: For what purpose do you need to use a hardener?

The dangers to a too-soft emulsion are almost always during processing and handling, i.e., before the wash, so it would make sense, if the goal is to reduce such damage, to harden the film at the earliest practical point in the processing sequence.

If you are trying to harden the emulsion to prevent damage after the film has dried, I don't think you will achieve much of an advantage. The dry emulsion is fairly hard, and I don't think having used hardener makes a huge difference after the film has dried. Its primary purpose is to keep the gelatin from swelling and softening so much when wet. (Michael R. and others, feel free to correct me if I'm wrong here!)

So, what gives?

Best,

Doremus

[Michael R]

Hi Doremus, my understanding is the same as yours regarding the purpose of hardening. Other than high process temperatures, according to the literature (Haist, James etc.) and manufacturer tech sheets the purpose of post-development hardening (usually in the fixer) was to prevent swelling/damage during the wash. Contemporary films don’t need this as they are pre-hardened. Reportedly Foma film emulsions are less hardened than Kodak/Ilford/Fuji but I don’t know whether or not that is correct.


xkaes,

I'm obviously in error about hardener not affecting fixing times too much. So, yes, that would be a consideration.

This whole conversation begs the question: For what purpose do you need to use a hardener?

The dangers to a too-soft emulsion are almost always during processing and handling, i.e., before the wash, so it would make sense, if the goal is to reduce such damage, to harden the film at the earliest practical point in the processing sequence.

If you are trying to harden the emulsion to prevent damage after the film has dried, I don't think you will achieve much of an advantage. The dry emulsion is fairly hard, and I don't think having used hardener makes a huge difference after the film has dried. Its primary purpose is to keep the gelatin from swelling and softening so much when wet. (Michael R. and others, feel free to correct me if I'm wrong here!)

So, what gives?

Best,

Doremus

[Alan9940]

Reportedly Foma film emulsions are less hardened than Kodak/Ilford/Fuji but I don’t know whether or not that is correct.

In my experience, Foma and EFKE films are indeed softer emulsions and use of a hardener in the fixer is worthwhile.

[Rick A]

In my experience, Foma and EFKE films are indeed softer emulsions and use of a hardener in the fixer is worthwhile.

Yes, but if you use a Pyro developer, which has a tanning effect on the emulsion, it negates the need for a hardener.

[xkaes]

So, what gives?

Best,

Doremus

I was looking at some formulas for hypo & fixer, and became interested in the fixing time of sodium vs ammonia. Most people think it too long, but how long is too long.

I found a lot on "hypo vs fixer time", but when running across hardener formulas, I saw nothing on which is the best step to add it. I just find it odd that it is not listed all over the place -- unlike "how long to keep your fixer"

[phdgent]

I thought that nowadays the need for a hardener wasn't necessary anymore as the modern thin emulsion films are less prone to mechanical damage. And that hardener unnecessarily extended the fixing- and washing time.

[Michael R]

I thought that nowadays the need for a hardener wasn't necessary anymore as the modern thin emulsion films are less prone to mechanical damage. And that hardener unnecessarily extended the fixing- and washing time.

Correct. There can potentially be some cases (see Alan’s note on Foma/Efke) where a hardening fixer might have a slight benefit if you anticipate damaging the film during washing. Generally speaking hardening fixers are a remnant of the past. Ilford doesn’t sell a hardener for Hypam anymore etc.

[xkaes]

I thought that nowadays the need for a hardener wasn't necessary anymore as the modern thin emulsion films are less prone to mechanical damage. And that hardener unnecessarily extended the fixing- and washing time.

That's what I'm assuming as well. But I'm not the only one that uses old emulsions, and, as mentioned, there can be other reasons to use a hardener. My "what I thought would be a simple" question was IF a hardener is used, at WHAT STEP is it best used.

[Doremus Scudder]

... My "what I thought would be a simple" question was IF a hardener is used, at WHAT STEP is it best used.

So, back to square one :)

Traditionally, soft emulsions that were prone to swelling and becoming damaged during a long wash were hardened in the fixing step, hence all the formulas for hardening fixers.

High-temperature processing (e.g., in the tropics w/o air conditioning, etc.) posed the risk of physical damage during development and stop steps as well, so prehardeners intended to be used before development were used.

Of course, it's possible to mix up a hardener and use it at any point in the process. There are a number of formulae for hardening stop baths such as Kodak SB-4 with pot. chrome alum and sod.sulfate, which seems to be used by a few here and over on the LF forum for Foma and Efke films.

I would imagine that identifying the point in the processing that posed the risk of damage to a soft-emulsion film would dictate just when in the sequence the use of hardener would be most beneficial.

Although a hardener in the fixer increases both fixing and washing times, it seems a better choice than a separate hardening step after the fix, since that takes time as well, plus an extra tray or holding vessel or whatever, which makes simply extending the fixing time the easier choice.

A hardening step after the stop but before the fix also seems superfluous, especially since it could easily be done at the stop-bath step. I've never seen a developer formula with a hardener incorporated; it seems that if such is needed, a prehardener is called for.

I guess the use of hardener these days is on an only-if-needed basis and where in the processing sequence it gets used depends on which step poses the greatest risk of damage to the film.

Best,

Doremus